Hand laying carbon fiber in a mold? Difficult? Any tricks or tips?

[spray2020]

A friend of mine is interested in one of my spoilers that I cast by hand, but instead of wanting one out of fiberglass he wants one made using carbon fiber. I have never worked with carbon fiber in a mold before (only overlays), and I figured it would work best if used with infusion and or vacuum bagging versus hand layup? (I dont have either of these more advanced methods setup) I dont own a compressor or a spray gun so everything is done all my hand and a brush.

I am afriad of ruining his carbon that he has sent to me because I am not sure how well it will conform to all of the tight radiuses/corners and interior edges by hand layup and no pressure keeping it in place. Also, is a clear gelcoat needed for a nice finish? What about laying down a layer of resin first before the layup and letting it cure before adding the carbon versus just laying down the carbon from the beggining? This is purely an aesthedic piece to him and he seems to care about the end finish the most. Does the finish of carbon fiber look clearer with epoxy or polyester?

I have some sample photos of my spoiler negative molds, showing how I typically lay up my spoilers with them open and also with them closed. With the molds open it allows me to easily get in to all the areas, but in the end leaves pinholes around the seams, versus laying them up closed it is harder to get into all the seams but leaves no pinholes around the seams at the end.

here are some photos molding it out of polyester gelcoat + polyester resin with both chopped strand mat and woven strand with the molds OPEN:

and here is a photo showing how tight the mold is to get into when it is laid up closed:

some photos of the finished part made with the molds OPEN (when the seams are sanded it reveals the resin at the seams)

[spray2020]

and here are some photos of that spoiler painted:

Any advice would be greatly appreciated! If what I plan on attempting is too difficult with my methods, please let me know!

[2talljohn]

I’d recommend vacuum infusion.

You’ll need vacuum bags, hoses, peel ply, sealant tape, and a vacuum pump. I never tried wet laying parts with such tight radi but maybe somebody else here has successfully done that?

Just to begin you are looking at spending a little bit of cash. Harbor freight has decent pumps that last a good amount of time. Everything else you can get from fiberglasssupplies. I think thats the company name.

For the carbon fiber I’d recommend going to solar composites.

Lastly to keep the fabric down in those areas when laying up, you should use super77. Not allot, just enough to keep the fabric in place. If the fabric lifts from the corners that’s ok, the bag will push everything down.

[susho]

Those are tight corners, but not impossible. without a vacuumbag it will be more difficult, but it can be done, as far as I can see.
I would lay a very thin glass layer first, to prevent pinholes in the surface. To keep you resin content “acceptable” I would laminate on baking paper, or a piece of plastic, wih a plastic spatula, squeegee, or something like that.
keep the fibres in +/- 45 degrees to the corners, this wil make it a lot easier… you can transfer the carbon on to the mould with the paper or plastic still attached, this will prevent your weave distorting, and your weave falling apart, making a big mess all at once.
Letting the first layer of fibre gel, will prevent it from distorting later when you continue your layup.
When you cant get your fibre in the tight corners, try a black pigmented fillet.
when you apply it tidy you will hardly notice it, and when you do, it looks better than badly laminated fibres

Just try it a few times, even testpieces will help you understand different techniques better. don’t expect it to turn out perfect the first time, practice makes perfect

[spray2020]

I’d recommend vacuum infusion.

You’ll need vacuum bags, hoses, peel ply, sealant tape, and a vacuum pump. I never tried wet laying parts with such tight radi but maybe somebody else here has successfully done that?

Just to begin you are looking at spending a little bit of cash. Harbor freight has decent pumps that last a good amount of time. Everything else you can get from fiberglasssupplies. I think thats the company name.

For the carbon fiber I’d recommend going to solar composites.

Lastly to keep the fabric down in those areas when laying up, you should use super77. Not allot, just enough to keep the fabric in place. If the fabric lifts from the corners that’s ok, the bag will push everything down.

Hey thanks for the advice for a quick overview on setting up vacuum infusion. I would love to set it up, however I am leaving the states within a month and a half and I am not sure that I should spend the time/money for the setup and then leave! I figured that super77 would be a good thing to use, thanks for the tip.

Those are tight corners, but not impossible. without a vacuumbag it will be more difficult, but it can be done, as far as I can see.
I would lay a very thin glass layer first, to prevent pinholes in the surface. To keep you resin content “acceptable” I would laminate on baking paper, or a piece of plastic, wih a plastic spatula, squeegee, or something like that.
keep the fibres in +/- 45 degrees to the corners, this wil make it a lot easier… you can transfer the carbon on to the mould with the paper or plastic still attached, this will prevent your weave distorting, and your weave falling apart, making a big mess all at once.
Letting the first layer of fibre gel, will prevent it from distorting later when you continue your layup.
When you cant get your fibre in the tight corners, try a black pigmented fillet.
when you apply it tidy you will hardly notice it, and when you do, it looks better than badly laminated fibres

Just try it a few times, even testpieces will help you understand different techniques better. don’t expect it to turn out perfect the first time, practice makes perfect

Also thanks for the reply. So a then glass layer first? A layer of the chopped strand or woven mat? Wouldn’t this block the carbon fiber from being 100% visible? Thanks for the tip about the backing paper, I tihnk I will try that out. After seeing my mold, would you attempt this with the molds open or would you lay it up with them closed? Could I use a mixure of a blackgelcoat/resin or gelcoat alone for the fillet?

[spray2020]

I just found an article on this silicone assisted compression method of backing the carbon fiber with a slightly smaller silicone inner backing mold to give pressure to all of the tight corners… however I dont think my mold has the proper surface for clamping against

what do you guys think?

http://johnsblogworld.blogspot.com/2010/11/making-carbon-fiber-case-using-silicone.html

[dallasb84]

i have an idea but… try at your own risk…i have done it successfully in similar situations.

get some handi foam spray insulation from the hardware store. a jar of petroleum jelly. and a steak knife.

it already sounds bad but…

if you have a spoiler thats already made take a brush and brush in petroleum jelly into the inside of it real thick. then spray in the foam into the bucket and let it fill it up. understand the stuff will expand so a little goes a long way.

let it dry and draw a line so you can trim it with the steak knife.

now when you go ahead and lay up the carbon you will have a foam plug to clamp in there. i wouldnt really worry so much as to having to pull it out as it wont add weight or anything like that but it will keep the carbon in place and will probably keep it nicely pushed in. cheap easy and effective in my honest opinion…